Any good cures for a dog that "marks?"

[Longhorn]

My favorite dog, Buddy, the white lab mix, will lift his leg and mark anytime there's something left on the floor, like my backpack or a laundry basket or a shopping bag. He also marks the couch, wastebasket, etc. -- things that are always there. We have four dogs, three males and a female, all of whom have been neutered/spayed for years. I clean it up as soon as I notice and have tried spraying with one of those sprays that's supposed to aid in housekeeping but it doesn't seem to work.

By the way, we know it's Buddy because Sparky squats when he pees, even though he's a male, and Brutus, the dachshund, is too short to reach some of the heights we've seen of the stream. Plus, we've caught Buddy in the act a couple of times. He's fully housebroken otherwise.

Thanks for your advice!